An electric power steering apparatus (EPS) serves as an apparatus which is equipped with a motor in a driving section. The electric power steering apparatus which provides a steering mechanism of a vehicle with an assist torque by means of a rotational torque of the motor, applies a driving force of the motor to be controlled with an electric power supplied from an inverter to a steering shaft or a rack shaft by means of a transmission mechanism such as gears. In order to accurately generate the assist torque, such a conventional electric power steering apparatus performs a feedback control of a motor current. The feedback control adjusts a voltage supplied to the motor so that a difference between a steering assist command value (a current command value) and a detected motor current value becomes small, and the adjustment of the voltage applied to the motor is generally performed by an adjustment of duty command values of a pulse width modulation (PWM) control. A brushless motor, which has excellent endurance and maintenance performances, and less undesired sound and noise, is generally used as the motor.
A general configuration of the conventional electric power steering apparatus will be described with reference to FIG. 1. As shown in FIG. 1, a column shaft (a steering shaft, a handle shaft) 2 connected to a steering wheel (handle) 1, is connected to steered wheels 8L and 8R through a reduction gear 3 in a reduction section, universal joints 4a and 4b, a rack and pinion mechanism 5, and tie rods 6a and 6b, further via hub units 7a and 7b. Further, the column shaft 2 are provided with a torque sensor 10 for detecting a steering torque Th and a steering angle sensor 14 for detecting a steering angle θ, and a motor 20 for assisting the steering force of the steering wheel 1 is connected to the column shaft 2 through the reduction gears 3. Electric power is supplied to a control unit (ECU) 30 for controlling the electric power steering apparatus from a battery 13, and an ignition key signal is inputted into the control unit 30 through an ignition key 11. The control unit 30 calculates a current command value of an assist command (steering assist) based on the steering torque Th detected by the torque sensor 10 and a vehicle speed Vel detected by a vehicle speed sensor 12, and controls a current supplied to the motor 20 for EPS based on a voltage control command value Vref obtained by performing compensation and so on with respect to the current command value.
As well, a steering angle sensor 14 is not indispensable and may not be provided. It is possible to obtain the steering angle sensor θ from a rotational position sensor such as a resolver connected to the motor 20.
A controller area network (CAN) to send/receive various information and signals on the vehicle is connected to the control unit 30, and it is also possible to receive the vehicle speed Vel from the CAN 40. Further, a non-CAN 41 is also possible to connect to the control unit 30, and the non-CAN 41 sends and receives a communication, analogue/digital signals, electric wave or the like except for the CAN 40.
FIG. 2 shows a power transmitting mechanism example of the motor 20 of the electric power steering apparatus and a connection example of the motor 20 and the control unit (ECU) 30.
As shown in FIG. 2, an output shaft 21 of the motor 20 is extended to an exterior of a motor housing 22, and the motor housing 22 to form a motor yoke includes a case body 23, which has an almost cylindrical configuration with a bottom surface and receives the motor body having a rotor and the like, and a motor attaching section 24 attached to an opening side of the case body 23. The motor attaching section 24 is in a disk form as an overall, and protrudes the output shaft 21 exterior to the motor attaching section 24 via a through hole in the center portion. The motor attaching section 24 may be in a flange form.
A power transmitting mechanism 50 coupled to the motor 20 includes a worm reduction mechanism comprising a worm 51 and a worm wheel 52, and has a coupling section 53 to couple the worm reduction mechanism to the output shaft 21. The worm 51 is formed in a middle portion of the worm shaft 51A being concentrically arranged in the output shaft 21 and is engaged with the worm wheel 52. The upper-side (handle) output shaft 2A of the column shaft 2 which integrally rotates with the worm wheel 52, is coupled to the concentric center of the worm wheel 52. The rotation of the motor 20, that is the rotation of the output shaft 21, is reduced and is transmitted to the upper-side output shaft 2A via the worm reduction mechanism.
An inside space of the motor attaching section 54 of the reduction mechanism side has a horn shape which gradually becomes a large diameter toward the motor 20 side (the opening side). Since the motor attaching section 54 is fixed to the motor attaching section 24 of the motor 20 side via a bolt, the opening of the motor attaching section 54 is sealed. The coupling section 53 and the output shaft 21 are positioned to a concentric center of the inside space of the motor attaching section 54 in a state that the motor 20 is attached to the motor attaching section 54 as shown in FIG. 2. The motor attaching section 54 is also in a corresponding flange form in a case that the motor attaching section 24 is in a flange form.
The motor 20 and the control unit (ECU) 30 or an ECU board are wired with a space via a lead wire 31, and the motor 20 is driving-controlled by the control unit (ECU) 30 via the lead wire 31.
In such the electric power steering apparatus, it is known the constitution that electric conductive parts such as a wiring board or bus bars are disposed near the coil of the motor, and the motor coil is electrically connected to an external power supply via the above parts.
Japanese Unexamined Patent Application Publication No. 2013-90376 A (Patent Document 1) is disclosed as a patent of the prior art. The constitution of Patent Document 1 is that: the control board is disposed at the anti-load side of the motor, a hole is necessarily existed in the motor case for disposing the bus bars, and the bus bars are protruded to the anti-load side.